1. Field of the Invention
The present invention relates to a method of and an apparatus for supplying a developing solution onto a photosensitive film which is formed on a substrate and developing processing is performed.
2. Description of the Background Art
A developing apparatus is used to develop a photosensitive film which is formed on a substrate such as a semiconductor wafer, a glass substrate for liquid crystal device, a glass substrate for photomask and an optical disk.
For example, a developing apparatus of spin type comprises a spin/hold portion for holding a substrate horizontally and rotating the substrate about a vertical axis, and a developing solution dispensing nozzle for supplying a developing solution to a surface of the substrate. The developing solution dispensing nozzle is attached to a tip end of a nozzle arm which is disposed for free rotation within a horizontal plane, and can move between an upper position above the substrate and a standby position.
During developing processing, after the developing solution dispensing nozzle moves to a position above the substrate from the standby position, a developing solution is supplied onto the photosensitive film which is formed on the substrate. As the substrate is rotated, the developing solution which is supplied spreads out over the entire surface of the substrate and contacts the photosensitive film. The substrate, as it holds the developing solution thereon (i.e., with the developing solution built up on the substrate) due to the surface tension of the developing solution, is kept still for a certain period of time, whereby the photosensitive film is developed. After the supply of the developing solution is completed, as the nozzle arm revolves, the developing solution dispensing nozzle moves to the standby position from the position above the substrate.
If the developing solution in the vicinity of an dispensing opening of the developing solution dispensing nozzle is exposed to air, the concentration of the developing solution changes because of the evaporation of the moisture contained in the developing solution and the properties of the developing solution change because of the contact of the developing solution with air. Hence, before the developing processing, the developing solution near the dispensing opening of the developing solution dispensing nozzle is expelled (i.e., pre-dispensing) in advance at the standby position, so that the developing solution which is supplied into the developing solution dispensing nozzle is homogenized.
However, in the conventional developing apparatus of spin type described above, when the developing solution hits the rotating substrate at the start of the dispensing of the developing solution, the photosensitive film on the substrate is subjected to a large impact. The impact creates air bubbles in the developing solution, and fine air bubbles which remain at a surface of the photosensitive film become development defects in some cases. Further, the impact of the developing solution at the start of the dispensing may damage the photosensitive film.
In addition, after the pre-dispensing, while the developing solution dispensing nozzle moves to the position above the substrate from the standby position, the developing solution in the vicinity of the dispensing opening of the developing solution dispensing nozzle contacts air. Due to this, it is possible that the properties of the developing solution which is supplied onto the substrate immediately after the start of the dispensing will change somewhat from those of the developing solution which is supplied successively and subsequently. Hence, development defects may be created on the substrate which contacts the developing solution which is supplied immediately after the start of the dispensing. Further, there is a possibility that the developing solution will dry out due to contact with air and the dried developing solution will adhere on the substrate as particles.
Moreover, since the developing solution becomes inhomogeneous during a process in which the developing solution which drops onto the substrate spreads out over the entire surface of the substrate because of centrifugal force, it is necessary to supply a large quantity of the developing solution until the developing solution on the substrate becomes homogeneous.